- The
Schwarzschild black hole
is the simplest ideal
black hole:
i.e., black hole
**NOT**affected by perturbations. (Actually, all real black holes are affected by perturbations to one degree or another.) The Schwarzschild black hole has zero angular momentum. and zero electric charge. Its structure is entirely determined by its mass and it is exactly spherically symmetric. - Virtually all astronomical objects
have rotation because
the processes of formation virtually always have inward swirl,
**NOT**a straight in radial, collapse. There the ideal Schwarzschild black hole probably**NEVER**occurs.However, Kerr black holes (i.e., rotating black holes) when rotating slowly enough approximate Schwarzschild black holes.

- Kerr-Newman black holes are those
with
**NON-ZERO**angular momentum and net electric charge (Shapiro & Teukolsky 1983, p. 357).Usually, macroscopic bodies in the universe are nearly neutral because any charge imbalance quickly attracts neutralizing charge. Thus, black holes that show significant Kerr-Newman black hole behavior seemed unlikely to exist. However, since circa 2015, it is hypothesized that Kerr-Newman black holes do exist and may have observable effects: e.g., as the sources of some fast radio bursts (FRBs) (see, e.g., Liu et al. 2016). So there may be mechanisms to significantly charge black holes and keep them charged.

- In fact, all real black holes to some degree or other
can be modeled as
Schwarzschild black holes.
- The
black hole singularity
(which is a gravitational singularity)
at the center of the
Schwarzschild black holes
is a point of infinite
density and finite
mass
(i.e., a "real" point mass).
In fact, the black hole singularity probably does

**NOT**exist. Quantum gravity effects (**NOT**included in general relativity) probably prevent the existence of gravitational singularities. But probably some super-dense state of mass-energy exists at the center of black holes---perhaps it has something like the Planck density ρ_Planck = c**5/(G**2*ħ) = 5.15500*10**93g/cm**3. - The event horizon is located
at the
Schwarzschild radius R_sch = 2GM/c**2
= (2.9532 km)*(M/M_☉)
= (19.741 AU)*[M/(10**9*M_☉)].
The event horizon is the point of no return. Nothing can escape from within the event horizon,

**NOT**even light.The light rays in the diagram start from vanishingly close to the event horizon,

**NOT**within it. From within it, there is**NO**path out (see Wikipedia: Event horizon: Event horizon of a black hole).The diagram shows that the non-radial outgoing light rays will be gravitational lensed back to the event horizon and they will

**NEVER**emerge.A outgoing nearly radial light rays will be gravitational redshifted by reaching infinity to nearly to zero photon energy E=hν

- Note the event horizon is, in fact,
the defining characteristic of
black holes no matter what
theory of
gravity is the
true macroscopic
emergent theory
of gravity,
general relativity or something
better that we know
**NOT**of yet. - The
curvature of space outside the
event horizon is such that
relative to the
Schwarzschild black holes center
change in circumference
is smaller than change in radius: i.e.,
ΔC < 2πΔr.
As you go to infinity, you recover the
Euclidean geometry
ΔC = 2πΔr.
Note the referred to distances are what you measure with a rigid ruler at one instant in time.

What of the curvature of space inside the event horizon? Let's

**NOT**worry about that now. - For reference, the
Schwarzschild radius formulae
are given below
(local link /
general link: black_hole_schwarzschild_radius_formulae.html):
- EOF

- See Black hole keywords
below
(local link /
general link: black_hole_keywords.html):
- EOF